August 2017: Looking Back at Harvey 5 Year Later

[Scott747]

If the 0z runs continue to show the northerly trend or at least stay consistent, the 1 am update should at least show a upward curve and a possible mention that those along the lower Texas coast (Mexico as well) should monitor.

Sometime tomorrow PTC advisories could be initiated if modeling doesn't do a 180.

[Rip76]

When Jeff and Srain are quiet.

[DoctorMu]

Be careful what you wish for! It's going to be an interesting week - very complicated forecast.

[srainhoutx]

Monday evening briefing from Jeff:


Tropical storm or hurricane threat to the TX coast late this week

The strong tropical wave formerly known as Harvey have continued to show increased signs of organization today, but there is no evidence of a defined low level circulation and convection has been decreasing this evening. Surface observations suggest that a broad circulation is found generally ESE of where the deep convection has been found today moving generally toward the WNW or in the direction of the southern Yucatan.

Expect the tropical wave axis to reach the eastern coast of the Yucatan on Tuesday and then emerge into the southern Gulf of Mexico early Wednesday. The well defined upper level low pressure system over the central Gulf of Mexico continues to move westward and will reach the NW Gulf late Tuesday into Wednesday and begin to weaken into a large weakness or shear axis. In other words this feature will break down the remaining ridging over TX and the NW Gulf allowing a trough across the central US by late week to push a frontal boundary deep into the state. This weakness in the ridge appears enough now to turn “Harvey” NW over the Gulf of Mexico with landfall potential from near Tampico, MX to Matagorda Bay, TX. The GFS has become the northern outlier today with a track toward Port Aransas while the CMC is the southern outlier with a track toward Tampico, MX and the ECMWF showing a landfall between BRO and CRP. At this point it is not overly important to focus on individual operational model runs, but instead the trends and the model ensembles. The trends today have been a general more northward track from an early morning consensus in NE MX to a late afternoon consensus over S TX. The CMC, GFS, and ECWMF ensembles are generally aimed at NE MX/S TX.

Much will depend on where a “new” center forms once the wave reaches the Gulf of Mexico early Wednesday. Should the surface center form northward along the wave axis a track toward the middle or upper TX coast would be possible, while a center formation toward the northern Bay of Campeche would likely result in a track toward NE MX/ S TX. It is impossible to determine at this time where any center may form which leads to a low amount of confidence.

One aspect noted in the model trends today is that even with a NE MX landfall the remains of the system get brought northward into SC TX this weekend and collide with the stalled frontal slop over the region. Both the GFS and ECMWF show the outbreak of a fairly significant rainfall event as the remains linger over coastal TX for 3-4 days post landfall and interact with the stalled frontal boundary. This trend can be noted in the “EPS” tracks below showing varying directions and looping motions over TX later in the forecast period indicating a system that is trapped in weak steering flow aloft.

Conditions appear generally favorable for intensification over the Gulf of Mexico with most models showing the formation of a 200mb high pressure cell over the system by the middle of the week helping to vent the surface center and preventing any sort of wind shear. Water temperatures are certainly warm enough to support intensification. The only drawback to intensification will be the 48-60 hours over the Gulf waters, but if conditions are ripe we have certainly seen storms in the past increase 40-60mph in that amount of time. For now will cap the intensity near a strong tropical storm, but a hurricane is certainly possible especially if the system develops quickly after leaving the Yucatan.

Note: NHC has tasked a high altitude mission tomorrow evening across the Gulf of Mexico to sample upper air steering patterns and have 3 USAF missions planned for Wednesday

Tropical Storm or Hurricane watches and warnings may be required for portions of the MX/TX coast as early as Wednesday.

Impacts:

For now will only raise rain chances starting Thursday and hold them high into the weekend and likely will need to closely monitor trends in amounts over the next few days. Will likely have to start pushing up tides starting Thursday, but not sure how high they may go at this point. Seas will almost certainly need to be raised from the flat-2ft currently over the coastal waters. Likely will see 6 ft by Thursday and could likely double that for Friday and Saturday for portions of the TX waters especially south of Matagorda Bay.

Residents along the TX coast should review hurricane preparation plans and be prepared to enact those plans this week

[stormlover]

https://www.tropicaltidbits.com/analysi ... 0&ypos=141

Nam maybe la bound???

[Texaspirate11]

HGX DISCO Concerning Harvey

The buzz around the local offices has been about how the NWP model
suite is handling the evolution of what may become TC Harvey.
They are very aggressive in taking the remnants of Harvey across
the Yucatan tomorrow and placing them into the southern Bay of
Campeche by tomorrow night into Wednesday morning....eventually
taking a tropical storm or hurricane into the Valley and meandering
it across south/central Texas through the weekend. Granted that
this wave will be entering a less sheared environment as the
central Gulf wide cyclonic circulation/inverted trough moves into
the western Gulf...but much remains uncertain especially since
Harvey is currently a wave heading west towards the Belize
coastline. Have remained conservative on increasing POPS/impacts
from mid week onward due to very low confidence....primarily stuck
to the generic 30-40 daily precipitation chances until better
focus comes into play (that time affords) from the evolution of
this wave across the Yucatan peninsula. So...in essence...if the
deterministic runs pan out then it will become a very busy week
for south and central Texas. The other scenario of this wave/Harvey
moving into southern Bay of Campeche and then steering west into
central Mexico makes this a persistent forecast of partially cloudy
days...mid-upper 70s/low-mid 90s and late morning through afternoon
20 to near 40 POPs. Let`s prepare for the former and hope for the
latter scenario.....31

[stormlover]

https://www.tropicaltidbits.com/analysi ... 0&ypos=161

[TexasBreeze]

The model above has it slightly making more nw movement toward the end of the run and it is strengthening towards the coast then it ends. It can be used more for upstream forecasting than reliably for tropics.

[mcheer23]

GFS is so far a little more north than 18z

[Scott747]

0z gfs is further n and stronger

[Scott747]

Late Friday night almost parallel with Brownsville as a borderline hurricane. About 100 miles or so offshore.

[TexasBreeze]

Approaching coast and strengthening pretty good. This really is beginning a trend for TX...

[mcheer23]

Holy GFS.....

[Scott747]

Well this is quite an ugly run. A rapidly deepening hurricane saturday evening heading right for the mid texas coast

[TexasBreeze]

Major hurricane right offshore Corpus Christi moving nw!!!

[TexasBreeze]

Mind you there is not too much currently there and it is tracking over the Yucatan. What it does overnight into tmw could be a real key in what it ultimately does. It has had a history of convective bursts overnight lately.

[Andrew]

GFS would be a very rough outlook. Landfall along Matagorda Bay with RI occurring. What is even more concerning is this is only 4 days out from landfall. If the EURO shows a similar result tonight some precautions may need to get started.

[Cromagnum]

That GFS run...

[TexasBreeze]

Track wise it shifted just slightly north and east after landfall being along or just west of our county warning area. Maybe starting to be more consistent?
Were there any upper air flight missions run today for the models?

[Scott747]

Yeah if the Euro shows anything similar it will definitely be time to start alerting friens and family about the potential/possibility of an impact along the Texas coast.

Problem is unless they are trropical weather nerds it's going to be hard to properly explain, because tomorrow its still going to be an unclassified system (ex Harvey) untill any regeneration happens later in the evening at the earliest.